This invention relates to DC power supply devices, and in particular, to multi-output-type power supply devices using separately-exciting-type switching regulators.
Although switching regulators are known to be excellent in efficiency, compactness and requiring only low power supply devices, they are high in cost. Therefore, in a known multi-output-type DC power supply device used in a digital circuit device, the switching regulator is used merely for a certain output in view of the fact that the voltage variation of only one of the outputs, such as the output of 5 V., is required to be within .+-.1% but voltages of the other outputs, such as outputs of .+-.12 V. and .+-.24 V., are not required to be so high in stability.
In arranging a multi-output-type DC power supply device wherein the high stability of voltages of all outputs is required, which is desired for use in electronic copying machines and other devices, a plurality of switching regulators must be provided to stabilize respective output voltages. However, it is disadvantageous from the view point of cost and simplicity of the device that a plurality of similar circuits, such as a pulse oscillator or a pulse generator and a power circuit for the oscillator and a pulse-width modulation circuit for forming the switching regulator, are provided in the device.